The present invention relates to a cordless telephone system.
Cordless telephone systems have currently been in widespread use due to their excellent mobility. The system includes a base station interfacing the public or private switched telephone network and a cordless station for exchanging radio control signals with the base station to establish a connection. During a standby mode, the base station constantly scans several speech channels to detect idle channels. In response to a call request from the cordless station, the base station specifies one of the idle speech channels as a possible candidate and informs the cordless station of the identifier of the specified channel over the control channel and waits for a response from the cordless station until a prescribed period expires. On receiving this information through the control channel, the cordless station switches to the specified channel and checks for the availability of the specified channel. Because of different field intensities between the sites of the base station and cordless station, the latter may determine that the specified channel is not actually available. Under such circumstances, the cordless station switches to the control channel and repeats the transmission of a call request to the base station. Failing to receive a response from the cordless station before the prescribed period expires, the base station recognizes that the specified channel is not available and switches to the control channel to wait for the retransmission of a call request. In response to the retransmission, the base station specifies another idle channel and informs this channel identifier to the cordless station to allow it to perform a channel check on the newly specified channel. The process will be repeated until an available speech channel is detected. Similar situations occur when an incoming call is received from the network.
Therefore, the time taken to establish a connection is substantial if busy conditions are repeatedly encountered at the site of the cordless station.